Hydrogenative pyrolysis of waste tyres: kinetic analysis

摘要

A kinetic model for the hydrogenative liquid-solid pyrolysis of waste tyres is presented. The model is tested with available experimental data obtained by running the pyrolysis of tyre particles (size < 500 μm) in a stirred batch reactor, in the presence of tetralin (as hydrogen donor), under a nitrogen atmosphere, and in the temperature range 345-430℃. Because a huge number of products is formed during the pyrolysis process, the compounds have been classified into homogeneous groups. On the basis of the proposed model, a reaction network which describes the evolution of these groups has been set. The kinetic constants of the reactions entering the network have been evaluated at 345, 393, and 430℃. The analytical equations obtained from the model fit the data satisfactorily. The results of the investigation indicate that the first step of the pyrolysis is the rupture of weak bonds which leads to the dissolution of the tyre particles as large aggregates of molecules, in a time which is of the order of 1 min. Then, much more slowly, lighter products are released from these aggregates. At T = 430℃ the large aggregates are completely transformed into stable compounds, detectable by GC, in about 250 min. At lower temperatures, T = 345℃, after 250 min of the loaded tyre is still present as macromolecules not detectable by GC.